1. Technical Field
The present invention relates to an airbag device, and relates particularly to an airbag device having a holding member configured to maintain a folded shape of a folded airbag.
2. Related Art
Airbags are in widespread use as means for improving the safety of an occupant and the like in a travelling vehicle. An airbag is installed at a driver's seat, a front passenger's seat, a seatback, and/or a roof side rail of an automobile to buffer the impact received by the head, chest, waist, or knees of an occupant coming into contact with an interior component upon a frontal collision or a lateral collision. Moreover, in recent years, an airbag installed at a front cowl portion for protection of pedestrians is under development for practical use.
An airbag is installed in a vehicle while normally being folded, and in often cases, they are never used throughout the life of the vehicle. An unused airbag constantly occupies an airbag installation space in a vehicle until a possible event when it is needed. An attempt for space saving and size reduction of an airbag device has been made so as to enable a layout having a good balance between an appropriate place inside an instrumental panel containing display devices for, for example, an engine, a motor, and the like which are functions used regularly and a place near an occupant which is preferable in view of improvement in convenience. Above all, an airbag device for a driver's seat is often installed in a center pad of a steering wheel, and the center pad is preferably compact in consideration of ease of viewing a speed meter and the like and in consideration of steerability. A compact center pad also enables a sporty design.
An airbag for the driver's seat is therefore folded compactly and placed in the center of the steering wheel while being covered by an airbag cover. A method for holding such a folded airbag with a holding member is used so that the folded airbag can be easily treated with a certain work in an assembling process and can be provided with stable quality.
Japanese Patent Application Publication No. 2006-27374 proposes an airbag device including the following airbag and airbag wrapper. Specifically, the airbag has a bag shape and includes an inlet opening through which an inflation gas enters the inside of the airbag. The airbag is folded as follows. A straight line passing through the center of the inlet opening along an opening plane of the upper side of the inlet opening is used as an arrangement reference line. Both ends of a folded body immediately before being completely folded, which extend to the respective sides from the arrangement reference line, are brought closer to the arrangement reference line and brought into face-to-face with each other at the arrangement reference line. The airbag is thus folded axisymmetrically into a complete folded body of a substantially cuboid shape, and is housed in this state. The airbag wrapper is formed of a flexible sheet material. The airbag wrapper is placed to surround the complete folded body so that the complete folded body can be prevented from being bent and losing shape. The airbag wrapper can also be broken upon inflation of the airbag.
The airbag wrapper includes: a covering portion having a to-be-broken portion located in a region above the arrangement reference line and configured to press the upper surface of the complete folded body; and fixing portions extending from the covering portion to both sides in a direction orthogonal to the arrangement reference line and configured to be fixed to the complete folded body.
The to-be-broken portion includes: multiple breaking openings penetrating from the front to the rear surfaces of the covering portion and capable of separating both edges of the covering portion extending in a direction of the arrangement reference line from each other upon inflation of the airbag; and joint portions configured to be opened upon breaking of the covering portion in such a manner as to connect the adjacent breaking openings.
The breaking openings each extend across the arrangement reference line to both sides of the arrangement reference line. The joint portions which are respectively located at one end and the other end of each breaking opening and thus adjacent to each other are located on opposite sides of the arrangement reference line.
At each of both edges of the covering portion in the direction of the arrangement reference line, an edge joint portion capable of being broken upon inflation of the airbag is interposed between the edge and the breaking opening located nearby, and a notch portion is provided. The two notch portions at the respective edges of the covering portion are arranged to be substantially symmetrical with respect to a point corresponding to the center of the inlet opening of the airbag on the arrangement reference line.